This invention relates to a method for determining whether the film stored in a new type of film cartridge is a developed film or an undeveloped one.
Ordinarily, a film is stored in a snail-shaped cartridge called "patrone" with the leading end of the film slightly protruding from the cartridge. Use of such conventional patrones involves various problems. Recently, a new type of cartridge was developed that is free of such problems. Such new type of film cartridge is disclosed in U.S. Pat. Nos. 5,347,334 and 5,031,852.
This film cartridge has a snail-shaped configuration like patrones but is smaller than patrones. It comprises two splittable parts so that the film wound around its spool can be taken out if necessary. It can store not only an unexposed film but also a developed and printed negative film.
An unexposed film is stored entirely in the cartridge prior to use. The film outlet is completely closed by a lid. When the cartridge is set in a camera, the film is fed out of the cartridge through its outlet by rotating the spool with the film outlet lid open.
The film trailing end is secured to the spool by engaging ribs protruding from a slit formed into the spool in holes formed in the trailing end of the film. The spool has flanges provided with edge members as film feed guides. Disposed between one of the spool flanges and the inner surface of the case is an arcuate disk plate carrying marks that indicate that the film is unexposed, exposed or developed, or bar codes for preventing double exposure.
FIGS. 15A-16B show this new type of film cartridge M. It is disclosed in the above-mentioned U.S. Patents. The structure of this film cartridge will be fully understood by referring to these patent documents.
As shown in FIG. 5, the film cartridge M contains a film take-up spool 101 in a snail-shaped cartridge case 100. Unlike patrones, the case 100 comprises two separable halves as shown. A door 102 is provided at a film outlet defined between the two halves when they are closed. Rotary shafts are connected to the spool 101 and the door 102 at one end of the cartridge. The respective rotary shafts are rotated by drive shafts that are inserted in holes 103 and 104.
At the end of the cartridge at which are the rotary shafts, an indicator plate 105 having a sector portion is provided. Differently shaped holes a-d are formed in an end plate 106 of the case. The holes a to d indicate that the film is unexposed (not photographed), partially exposed, exposed (but not yet developed), and developed, respectively. By rotating the indicator plate 105, its sector portion, colored white, can be brought into alignment with one of the holes a-d, so that the hole brought into alignment with the sector portion turns white. Thus, one can see the state of the film by checking which hole is colored white.
As seen in FIG. 15B, the film F around a spool shaft 101b of the spool 101 is entirely wound into the cartridge case 100 and completely shielded from light by closing the film outlet with the door 102. To expose the film, i.e. to take pictures, the door 102 is opened and the spool 101 is rotated to push the film F out of the cartridge.
To wind film F on the spool 101, as shown in FIG. 16B, the trailing end of the film F is inserted in a slit 107 formed in the spool shaft 101b until a rib 108 engages in a hole h formed in the film F near its trailing end. Then, the spool 101 is rotated. When the film is entirely wound around the spool 101, a cutout 109 formed near the leading end of the film F is caught by a skirt of the flange 101c and the film stops.
In order to develop and print a film stored in this type of film cartridge, the trailing end of the film has to be separated from the spool be fore feeding it into a developing or a printing machine. However, it is impossible to automatically separate the film from the spool. Thus, in order to effectively develop a film stored in such film cartridge, the film has to be rewound onto e.g. an intermediate cartridge.
A film winding device for winding a film into such an intermediate cartridge or a similar film take-up unit is disclosed in Unexamined Japanese Patent Publication 5-232633. This winding device has a film cartridge receptacle, and a film take-up unit spaced a predetermined distance from the receptacle. Film feed rollers and a film guide are provided therebetween and separate motors are provided for the film cartridge and the feed rollers.
The film is fed by rotating the spool in the film cartridge with a film cartridge motor until the film leading end is caught by the feed rollers. Thereafter, the film is fed to the take-up unit by rotating the feed rollers with the feed roller motor. When the film trailing end gets clear of the cartridge and the feed rollers, the respective motors stop. But due to the inertia of a flywheel provided between the spool and the film cartridge motor, the spool tends to keep rotating for a short while after the motors have stopped.
Due to this extra rotation of the spool, the rib will disengage from the hole in the film near its trailing end. In this state, the feed roller motor is reactivated to feed the film until its trailing end separates from the feed rollers. The film is thus separated from the spool in the film cartridge.
A similar device is disclosed in Unexamined Japanese Patent Publication 6-130633. The separator of "an engaging device and a separator for photographic film" disclosed in this publication has a release plate adapted to be inserted into the film cartridge through a film outlet formed in the cartridge case to disengage the trailing end of the film from a rib in a slit of a spool shaft.
This new type of film cartridge is designed to automatically feed film. A film is stored entirely in the cartridge, irrespective of whether the film is an exposed one or an unexposed one, unlike a patrone in which a film is stored with its leading end slightly protruding from the case. The leading end of the film is fed by rotating the spool.
It is impossible to visually check whether the film in such a film cartridge is developed or undeveloped. Instead, this is determined by checking the indicator plate provided near one end wall of the film cartridge as described above, or by checking whether or not the cartridge has a nail (hereinafter IPI nail or simply nail). If no nail is detected, the film is developed, and if detected, the film is not developed.
If an undeveloped film is mistaken for a developed film and exposed to light for e.g. printing, its images will be lost completely. The lost images might have been an invaluable asset for a customer. In order to prevent such an accident, it is highly desirable to double-check if each film is a developed one or not before it is fed out of the film cartridge.
But such a double-check method has not yet been established for this new type of film cartridge. Thus, in order to positively prevent such accident, it is necessary to double-check again if each film is a developed one or not before it is fed into a processing machine.
An object of this invention is to provide a method of identifying the film type which can positively identify the type of film stored in a film cartridge of the abovementioned new type.